National Repository of Grey Literature 52 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Photosynthetically produced hydrogen
Osipenko, Elena ; Němcová, Yvonne (advisor) ; Ráček, Jan (referee)
Bio-hydrogen from microalgae and cyanobacteria has attracted commercial awareness due to its potential as an alternative, reliable and renewable energy source. Photosynthetic hydrogen production from algae and cyanobacteria can be interesting and promising options for clean energy, because hydrogen is produced at ambient temperature and pressure and releases only water as a by-product. The energy of sunlight is used to split the water molecule into protons (H+), electrons (e-) and O2. The protons and electrons are then recombined with the help of the enzymes hydrogenase or nitrogenase (in the case of cyanobacteria) to form H2. Both of these enzymes are sensitive to O2 and therefore require the processes of H2 formation and CO2 fixation to be separated. This bachelor's thesis aims to describe the principle of H2 formation in different cyanobacterial and algal systems and mention the problems and limitations. The thesis also presents recent approaches, including genetic and metabolic engineering of cyanobacteria and algae or co-culturing of algae and bacteria, where an anaerobic environment is created by enhanced bacterial respiration.
Bioluminescence in Dinoflagellates
Zahradníček, Ondřej ; Němcová, Yvonne (advisor) ; Pichrtová, Martina (referee)
Bioluminescence is a relatively widespread phenomenon in nature. A variety of organisms have the ability to emit light. The aim of this bachelor thesis is to summarize the latest findings on bioluminescence in dinoflagellates. These organisms are the most important protist lineage capable of producing light flashes. Indeed, they are responsible for most of the bioluminescence observed in surface the seas and oceans. This bachelor thesis discusses the biochemical reaction of bioluminescence in which the substrate (luciferin) is oxidized in the presence of the enzyme luciferase. The thesis introduces the major species of luminescent dinoflagellates that frequently cause toxic harmful algal blooms. Then the factors affecting the intensity of bioluminescence are discussed. Last but not least, dinoflagellates can use bioluminescence as protection from predators. For example, they may use a flash of light to startle predators or use the flash as a "burglar alarm" to attract predators of their predators. Key words: bioluminescence, luciferin, luciferase, dinoflagellates, light flash
Micromorphology of segments in Halimeda tuna and their relation to calcium carbonate precipitation
Čečmanová, Adéla ; Neustupa, Jiří (advisor) ; Němcová, Yvonne (referee)
Algae of the genus Halimeda are important representatives of green algae, thanks to their ability to calcify. Calcification is the process of CaCO3 precipitation in the form of aragonite or calcite, which is then deposited on the bottom of the sea and thus participates in the formation of sedimentary rocks. Relatively small amount of information is known about calcification in representatives of the genus Halimeda, and in particular about its storage and distribution within the plant. One of the representatives of calcifying algae is Halimeda tuna living in the Mediterranean Sea, where it forms a significant part of the underwater vegetation. These algae have a thallus composed of segments, the internal structure of which is formed by utricles - a structure in which the aragonite is deposited. The aim of this work was to find out whether the different sizes of utricles within one segment have an effect on the subsequent spatial distribution of aragonite. The results showed that the distribution of aragonite microcrystals is not dependent on the size of the utricles - it is therefore equally spread across the segment. Furthermore, we investigated whether the calcification process would differ depending on the time of sampling during the year. From our data it appears that this process exhibits some...
Diversity and function of pattern structures in the microworld
Hirnerová, Anna ; Škaloud, Pavel (advisor) ; Němcová, Yvonne (referee)
This thesis summarizes current knowledge of patterns and structures at various scales, with an emphasis on the use of these patterns in the microworld and also on the materials that are most often used. Patterns are applied in all areas of natural processes and human activity. There are many analogous models at different scales, but we do not know if they have the same self-organizing mechanisms. Many patterns formed by microorganisms can be prepared without their presence, on the basis of physical and chemical methods, so they are probably created under certain parameters that can be influenced by a given protist. These patterns are evolutionarily advantageous for microorganisms, because they provide them with a number of functional adaptations, mainly in connection with defense against predators and movement in the water column, which is based on the organism's life strategy. The mathematical description of the pattern is extremely important for its further research and for determining the laws that have allowed the organism to benefit from its parameters. Keywords: pattern, structure, convection, reaction - diffusion model, geometry, protist, microorganism, skeletons, shells, scales
Pattern as a functional trait, case study on Mallomonas chrysophytes
Knotek, Petr ; Němcová, Yvonne (advisor) ; Rychtecký, Pavel (referee)
The patterns that can be admired on the surface of many living creatures are also found in many microscopic organisms outside of the macroscopic world we are familiar with. However, their significance and function are yet little understood compared to those of the macroscopic world. In diatoms (Bacillariophyceae) and coccoliths (Haptophyceae), several hypotheses have already been developed concerning the function of their patterned shells. One hypothesis considers the shell as a photonic entity that could reflect UV radiation away from the cell. Others focus more on its mechanical properties, which are among the most impressive within biological structures. Silica-scaled chrysophytes (Synurales, Stramenopiles) also possess a complex shell (or scale-case). Cells are covered with scales (about 4 µm in size) that are very regularly arranged and form a siliceous scale-case on the surface. The pattern on the scales is species-specific and has undergone gradual modification during evolution. This work aims to assess whether the patterning of siliceous scales in the order Synurales can be considered a functional trait or it is a result of neutral evolution. To test the possible photonic properties of the patterned structures, a pair of growth experiments were performed. The experimental cultures were...
Synura echinulata (Synurales) - silica scale plasticity in natural populations influenced by environmental factors; accompanying scaled chrysophytes
Kreidlová, Jana ; Němcová, Yvonne (advisor) ; Hodač, Ladislav (referee)
The silica scale shape variation in Synura echinulata has been investigated only in laboratory conditions, so far. The aim of this thesis was to study scale shape variation in natural populations and to determine which environmental parameters influence the scale shape. The scale shape variation was investigated using landmark-based methods of geometric morphometrics. Scale shape changes related to environmental factors were analyzed using the two-block method PLS (Partial Least-Squares analysis) and adonis (R). The scale shape was mostly influenced by locality, pH and altitude. Shape distinguished populations of S. echinulata probably exist in different localities. The more distant localities are, the less similar are scales of S. echinulata in their shape. This scale shape variation is probably genetically determined, even thought all so far sequenced populations belong to the same species. High morphological disparity which was probably caused by anthropogenic pollution, was recorded in the locality Brdy. During sampling of the natural populations of Synura echinulata in the Czech Republic, several localities representing a significant reservoirs of species diversity, were found. Therefore, the thesis was extended and biodiversity research in the Czech Republic was added. A few samples were...
Shape dynamics of silicate structures in experimental populations of chrysophytes (Synurophyceae)
Pichrtová, Martina ; Němcová, Yvonne (advisor) ; Elster, Josef (referee)
The aim of the proposed diploma thesis was to analyze temperature and pH related shape variation in synurophyte silica scales. Four species were investigated - Synura petersenii, S. echinulata, S. sphagnicola and Mallomonas tonsurata. The strains were cultivated in 5 different temperature levels. Moreover, S. petersenii and M. tonsurata were grown in 4 (resp. 5) different pH levels, too. The shape dynamics of the scales was investigated with application of landmark based geometric morphometric methods. The relative warps analysis described the overall shape and the main trends in morphological variation were depicted as deformation grids. The effects of both cultivation temperature and pH on the scale shape were significant, although only a small proportion of the overall variation was explained by the particular regression models. Moreover, the scale size of the investigated species decreased with increasing temperature (with the exception of Synura echinulata). These results are in agreement with the Atkinson's temperature rule which was formulated for the body size of ectotherms. The relationship between the size and pH was not explicit - the size of the scales decreased with increasing pH in S. petersenii, but increased in M. tonsurata. Furthermore, the scale shape was also found to be related to the...
Phaeocystis - a key organism in dimethylsulfoniopropionate production; ecological and physiological functions of DMSP
Füllsacková, Alena ; Němcová, Yvonne (advisor) ; Pusztai, Martin (referee)
Dimethylsulfoniopropionate (DMSP) is an organic sulfur compound with an important ecological and physiological functions. DMSP is a major precursor for dimethylsulfid (DMS). DMSP is produced by variety of halophytic plants and phytoplankton for the purposes of osmotic regulation, antioxidation and protection from predators. It is especially widespread among the marine phytoplankton and it is ubiquitous in the euphotic zone. DMS and DMSP are also involved in flux of carbon and sulfur. Marine emissions of DMS have a particularly important role as precursors of atmospheric sulfur-containing aerosols that influence the Earth's climate system through direct backscatter of solar radiation and through cloud formation. DMSP is produced mainly by phytoplankton, because this group of organism is very large, I'll focus on Phaeocystis. Phaeocystis is a genus of marine phytoplankton with a worldwide distribution. It has a polymorphic life cycle alternating free-living cells and colonies but develops massive blooms under the colony form. Among the 10 species, only 3 (P. pouchetii, P. antarctica, P. globosa) have been reported as blooming species. DMSP is produced intracellulary and it is released as DMS. DMS concentration is high during the growth of the cells, predation or senescence. The production of DMSP is...
The role of microhabitats in spatio-temporal differentiation of freshwater algal assemblages
Pusztai, Martin ; Němcová, Yvonne (advisor) ; Kulichová, Jana (referee)
This thesis deals with microhabitats in relation to the spatio-temporal differentiation of freshwater algal assemblages. Algae are defined ecologically, althought they represent a diverse polyphyletic conglomerate. Based on the available literature, type of substrate appears as a suitable representative of most freshwater microhabitats when comparing results from different studies. Influence of microhabitat may occur not only on a small spatial scale, but also on a regional scale. The importance of scale and traceability of different factors are further discussed as well as the appropriate definition of the microhabitat. Microhabitats diversity is often reflected in the spatial heterogeneity of algal assemblages. Based on the common trends in the algal life strategies, erosional and depositional substrates can be distinguished. Living substrates, especially macrophyte surfaces represent a special category of microhabitats. Algae can enter complex interactions with these living substrates.Temporal dynamics is relatively less explored in comparison with the spatial heterogeneity.

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